1. Field of the Invention
The present invention relates to a method for preparing optically active 3,4-dihydroxy butyronitrile and 3,4-dihydroxy butyric acid derivatives.
2. Description of the Prior Art
Hitherto the following two methods have been known as the preparation of optically active 3,4-dihydroxy butyric acid derivatives or 3,4-dihydroxy butyronitrile:
(1) The method of reducing dimethyl ester of L-malic acid by using boran dimethyl sulfide in the presence of a catalytic amount of sodium borohydride to convert into 3,4-dihydroxy butyric acid methyl ester (Japanese Laid-Open Patent No. 61-22049, Japanese Laid-Open Patent No. 63-22056, Chemistry Letters 1389, (1984); and
(2) The method of selectively hydrolyzing dimethyl ester of L-malic acid by using esterase (PLE), reducing by using boran dimethyl sulfide, and converting into 3,4-dihydroxy butyric acid methyl ester (Journal of Organic Chemistry, 50, 1145, (1985)).
On the other hand, as the preparation of racemic compounds, the following methods, among others, are known:
(1) The method of producing 3,4-dihydroxy butyronltrile by the reaction of racemic 3-chloro-1,2-propanediol with KCN in water, or successively treating with NaOH and HCl to convert into S-butyrolactone derivative (Compt. Rend. 238, 1231, (1954)).
(2) The method of causing recemic 3-chloro-1,2-propanediol to react with NaCN in water, and refining by using an ion exchange resin (J. Am. Chem. Soc., 197, 24, (1985)).
On these methods, the methods of producing optically active compounds use L-malic acid as the starting material, and also require boran dimethyl sulfide which is a relatively expensive reducing agent, and hence they involve various problems in economy and operation as the practical preparation of optically active 3,4-dihydroxy butyric acid derivatives.
On the other hand, the method of production of racemic 3,4-dihydroxy butyronitrile by cyanation of 3-chloro-1,2-propanediol is likely to produce by-products such as 3,4-dihydroxy amide and 3,4-dihydroxy butyric acid, and is poor in selectivity of reaction, and it involves various problems to be solved in the reaction selectivity, reaction yield and controllability, as the practical preparation of 3,4-dihydroxy butyronitrile.